Munition control system

ABSTRACT

1. A munition safing, arming and firing system comprising means for transmitting a code consisting of pulses of differing frequencies, means for receiving said code, means for segregating the received pulses according to frequency, a stepping relay having a plurality of contact decks each of which corresponds to one of the frequencies contained in said code and one additional contact deck, each of said contact decks having an associated wiper arm, said wiper arms being ganged for conjoint movement, means connected to said segregating means for applying ground potential to only one of the wiper arms of said plurality of contact decks, in response to a pulse of the corresponding frequency means interconnecting the contacts of said plurality of contact decks in correspondence with a preselected code, switch means for advancing said wiper arms one contact position in response to each pulse received by said receiving means, code check means connected to said interconnecting means for freerunning said stepping switch back to its initial position after a predetermined time delay in response to a pulse which deviates from said preselected code, time delay means connected to said code check means for free-running said stepping relay back to its initial position after a predetermined time independently of the receipt of an incorrect pulse, arming circuit means connected to a predetermined contact of said additional contact deck, firing circuit means connected to a contact succeeding said predetermined contact and to said code check means so that upon the receipt of a correct series of pulses followed by an incorrect pulse the firing circuit will be activated through said code check means.

United States Patent Kups June 10, 1975 MUNITION CONTROL SYSTEM saidcode, means for segregating the received pulses according to frequency,a stepping relay having a plu- [75] hwamor' ggn f Kups L05 Angelcsrality of contact decks each of which corresponds to one of thefrequencies contained in said code and one [73] Assignee: The UnitedStates of America as additional contact deck, each of said contact decksrepresented by the Secretary of the having an associated wiper arm, saidwiper arms being Army, Washington, DC. ganged for conjoint movement,means connected to [22] Filed: Sept. 10 1959 said segregating means forapplying ground potential to only one of the wiper arms of saidplurality of pp 839,264 contact decks, in response to a pulse of thecorresponding frequency means interconnecting the [52] CL 102/701;71140;:340117] contacts of said plurality of contact decks In corre-[511 Int. CL F426 "/00 spondence with a preselected code, switch meansfor 'dvancing said wiper arms one contact position in re- [58] Field ofSearch .4 102/702; 317/l40, [38, d

7/1381; 340/1164 71 sponse to each pulse recelved by said receivingmeans, code check means connected to said interconnecting [5M ay in re-UNITED STATES PATENTS sponse to a pulse which deviates from saidpreselected 2,5l4 889 /1 50 McGoffin a 340/164 code, time delay meansconnected to said code check 2-652J97 M953 Berger t A 317/140 means forfree-running said stepping relay back to its gg igz 3 7 initial positionafter a predetermined time indepen 2:912:66 ll/l959 Canto et al. 340/171demly of the recap of pulse am'mg Primary Examiner-Benjamin A. BorcheltAssistant Examiner-C. T. Jordan Attorney, Agent, or FirmNathan Edelberg;Robert P. Gibson; Saul Elbaum cuit means connected to a predeterminedcontact of said additional contact deck, firing circuit means connectedto a contact succeeding said predetermined contact and to said codecheck means so that upon the receipt of a correct series of pulsesfollowed by an incorrect pulse the firing circuit will be activatedthrough said code check means.

2 Claims, 1 Drawing Figure mm AM uTs; |-Tia| i; HFioTT.;u 35?,1521,Moouuroa I 'Wb I: W' MASTER I \cooso saciuu. r sung" I w 0 u A-MRECEIVER LOW TONE LA Z5 roue nan cone REVERSNC DEVICE MUNITION CONTROLSYSTEM The invention described herein may be manufactured and used by orfor the Government for governmental purposes without the payment to meof any royalty thereon.

This invention relates to improved means for arming, firing and safing(that is, disabling) a munition by means of a radiofrequency signalradiated to a munition control circuit from a master station located ata distance from the munition.

In the arming, firing and safing ofa munition at a distance by means ofa transmitted radiofrequency signal, it is necessary to code thetransmitted radiofrequency signal in such a way that the enemy cannotduplicate the signal and thereby cause premature operation of themunition. Also, it is necessary to prevent the enemy from sending a fewsimple codes to cause reject (error code) relays to operatecontinuously. Continuous operation of these relays would reduce the lifeof the battery power supply and make the unit inoperative. Accordinglyit is the broad object of this invention to provide improved means forarming, firing and safing a munition at a distance so that the munitioncan neither be prematurely detonated, nor can its power supply be rundown by an enemy.

Another object of this invention is to provide an improved munitioncontrol circuit operated at a distance by a transmitted radiofrequencysignal which, in addition to having the features of the above object,also incorporates fail-safe features to prevent accidental firing orarming of the munition in the event of failure of some component in theelectrical control circuit of the munition.

A further object of this invention is to provide improved means forsafing the munition at a distance by means of a properly chosenradiofrequency safing signal which disconnects anti-disturbance devicesand other active components in order to make the munition safe tohandle.

A still further object of this invention is to provide a munitioncontrol circuit which incorporates means for radiating a signal to themaster station after the munition has been made safe, thereby making itpossible to determine whether the transmitted safing signal has achievedits purpose.

Yet another object of this invention is to provide a munition controlcircuit having all of the above features which in addition is relativelysimple, compact and inexpensive.

In a typical embodiment of the invention, the above objects areaccomplished by means of a specially designed electrical control circuitfor the munition which permits arming, firing and safing only inresponse to specially chosen coded signals which amplitude modulate aradiofrequency carrier of predetermined frequency, transmitted from amaster station. A coded signal consists of a plurality of pulses, eachof which comprises high or low frequency energy, and separated by a timeinterval of no signal. These pulses of high and low frequency energymodulate the carrier in a predetermined sequence, such as low, high,low, low, high, low, high, etc., for example. The munition controlcircuit is designed to arm, fire or safe the munition only in responseto the receipt of the proper predetermined sequences of pulses. It is tobe noted that by requiring a proper sequence of say pulses, over millioncombinations are possible, only a few of these being used to operate themunition. By employing a stepping relay with a plurality of decks incombination with associated relays and other circuit components, thedesired code sequences are recognized from these 30 million combinationsand caused to arm, fire or detonate the munition in an amazingly simplemanner.

The specific nature of the invention, as well as other objects, uses,and advantages thereof, will clearly appear from the followingdescription and from the accompanying drawing, in which:

The drawing is a schematic and block diagram of a munition controlsystem in accordance with the inven tion. In describing and explainingthe operation of this invention in the clearest manner so that itsinventive features may be clearly revealed, no attempt will be made todescribe in detail the structural features of the circuit components ofthe interconnections therebetween. The circuit components employed areof well known types and readily providable by those skilled in the art,and the interconnections therebetween are clearly shown in the drawing,the invention residing chiefly in the combination of circuit componentsand the cooperation therebetween. Instead, the circuit components andtheir functions in the circuit will be summarized briefly, and this willbe followed by a detailed description of the various operations andfunctions provided by the invention which is believed to be entirelysufficient to enable one skilled in the art to make and use theinvention.

In the drawing, a master station 10 has a radiofrequency oscillator 11of predetermined frequency to which is connected an A-M modulator 13adapted to modulate the oscillator 11 with a coded signal fed to theinput of the modulator 13. The oscillator 11 feeds an antenna 8 whichtransmits the coded radiofrequency energy to an antenna 14 connected toan A-M receiver 12. The master station 10 is located at a first locationwhile the remaining circuitry shown in the drawing makes up the munitioncontrol circuit which is placed with the munition at a second locationat a distance from the first location. The master station 10 alsoincludes a receiver 17 connected to the antenna 8 and an indicator 24connected to the output of the receiver 17 to indicate the receipt of asafing signal transmitted from the munition control circuit.

The coded radiofrequency signal from the master station transmitter 10consists of a radiofrequency signal amplitude modulated by a sequence ofpulses, the pulses comprising energy of at least two differentfrequencies. In the preferred form of the invention now to be described,the coded pulses from the master station consist of a sequence of pulsesof high and low fre quency energy as illustrated, feeding the A-Mmodulator 13 of the master station 10 in the drawing. The terms high"and low are intended to designate pulses of energy having widelydifferent frequencies so as to be easily distinguishable.

The A-M receiver 12 is tuned to the predetermined carrier frequencytransmitted from the master station 10, and is adapted to detect thecoded signal modulating the carrier and consisting of high and lowfrequency pulses of energy. These detected pulses of energy are fed tothe low pass filter 16 and the high pass filter 18. The low pass filter16 passes only the low frequency pulses of energy, while the high passfilter 18 passes only the high frequency pulses of energy. A low tonerelay 25 has two normally open contacts 23 and 27 and a coil 21connected to the output of the low pass filter 16. Similarly, a hightone relay 35 has two normally open contacts 33 and 37 and a coil 31connected to the output of the high pass filter 18. In response to eachpulse of low frequency energy, therefore, the low tone relay 25 isenergized closing its contacts 23 and 27 for the duration of the pulse,while in response to each pulse of high frequency energy the high tonerelay is energized closing its contacts 33 and 37 for the duration ofthe pulse.

The heart of the munition control circuit consists of a stepping relay55 having a coil 51, a normally closed interruption contact 52, a homecontact 53 which is closed except when the relay 55 is in its homeposition, and three independent decks 56, 57 and 58, each having 25contacts and a movable arm 66, 67 and 68, respectively. The movable arms66, 67 and 68 of decks 56, 57 and 58, respectively, step synchronouslyfrom contact to contact in response to the application of pulses to thecoil 51, the stepping relay advancing one step after each pulse ofenergy is received. The interconnections between the contacts of thedecks 56 and 57 determine the coded sequence of high and low pulses ofenergy which will arm, fire or safe the munition, whatever the case maybe, while the contacts of the deck 58 interconnect various othercomponents.

Also provided in the embodiment of the drawing are a code reversingrelay 45, a code check relay 85, three time delay relays 75, 105 and135, a firing relay 115, a safing relay 125, and a relay 95. The codereversing relay has a coil 41, two single-pole double-throw contacts 46and 47, a normally closed contact 48 and a normally open contact 49. Thecode reversing relay 45 is used to reverse the code provided by thecontacts of decks 56 and 57 of the stepping relay in connection with thesafing operation of the circuit. The code check relay 85 has a coil 81,three single-pole doublethrow contacts 86, 87 and 88, and a normallyopen contact 89. The code check relay comes into operation when a wrongsequence of pulses is applied to the stepping relay 55. The time delayrelay provides a delay of 3 minutes, has a coil 71 and a normally closedcontact 72, and is utilized in connection with the opera tion of thecode check relay 85. The time delay relay 105 provides a delay of 1minute, has a coil 101 and a contact 106, and operates in cooperationwith the code check relay and the relay which has a coil 91 and anormally closed contact 96. The time delay relay 135 provides a delay of3 seconds, has a coil 131 and a normally open contact 136, and operateswith the code reversing relay 45 in connection with the safing operationprovided by the munition control circuit. The firing relay has a coil111 and two normally open contacts 116 and 117, and operates with thecode reversing relay 45 in connection with the safing operation providedby the munition control circuit. The safing relay has a coil 121, anormally open contact 126 and a single-pole double-throw contact 127,and operates in connection with the safing operation of the munition.

Further shown in the drawing is a firing circuit adapted to fire adetonator 170 when a suitable pulse is applied to the firing circuit150. In addition, an anti disturbance device is provided to fire thedetonator in the event that the munition is disturbed, such as byhandling in an attempt to disarm the munition by the enemy.Anti-disturbance devices are usually in the form of a switch whichcloses momentarily to fire the detonator 170 if the munition issubjected to a disturbance. A transmitter is connected to the antenna 14and is adapted to radiate a predetermined signal to the master station10 when the munition has been made safe.

The operation of the munition control system shown in the drawing willnow be described in detail. The master station 10 transmits aradiofrequency signal of predetermined frequency, amplitude modulated bya coded signal preferably consisting of high and low frequency pulses ofenergy, as described previously. These pulses are detected by the A-Mreceiver 12 tuned to the predetermined carrier frequency and then fed tothe low pass and high pass filters l6 and 18. A pulse of low frequencyenergy closes the contacts 23 and 27 of the low tone relay 25 for theduration of the pulse, while a pulse of high frequency energy closes thecontacts 33 and 37 of the high tone relay 35 for the duration of thepulse. The coil 51 of the stepping relay 55 has a first end connected toa grounded power source represented by the battery 240, and a second endconnected to the commonly connected moving arm elements 230 and 33a ofthe contacts 23 and 33 of the relays 25 and 35, respectively. Thecommonly connected fixed elements 23b and 33b of the contacts 23 and 33,respectively, are connected to circuit ground through the unenergizedcontact 86 of the code check relay 85. Thus, when either of the relays25 and 35 are energized by its respective low or high frequency pulse ofenergy, the coil 51 is energized for the duration of the pulse, therebycausing the stepping relay 55 to advance one step when the coil 51 is nolonger energized.

The code reversing relay 45 is initially unencrgized so that the movablearms 66 and 67 of the stepping relay decks 56 and 57, respectively, areeffectively connected to the movable arm elements 27a and 37a of thecontacts 27 and 37 of the relays 25 and 35, respectively, the fixedelements 27b and 37b being connected to circuit ground. It can thus beseen, therefore, that with the code reversing relay 45 unenergized, apulse of low frequency energy which energizes the relay 25 places aground on the movable arm 66 of the deck 56, while a pulse of highfrequency energy which energizes the relay 35 places a ground on themovable arm 67 of the deck 57.

The contacts 125 of each of the decks 56 and 57 of the stepping relay 55shown in the drawing are set up, for illustrative purposes, for thefollowing coded sequence of pulses:

(1) low, (2) low, (3) low, (4) low, (5) high, (6) high, (7)(l1) low,(l2)-(16) high, (17) low, (18) high, (19) low, (20) high, (21)(25) low.The terms low and high refer to pulses of low frequency energy andpulses of high frequency energy, respectively.

To now illustrate how the stepping relay S5 acts to provide operationonly in response to the receipt of the proper sequence of high and lowpulses of energy as given above, it will first be assumed that with thestepping switch in its home position as shown in the drawing, thefollowing wrong code sequence is received: 1) low (correct), (2) low(correct), (3) high (wrong), (4) high (wrong), and (5) to (25)(correct). The receipt of the first pulse (1 which is low, thus places aground on the movable arm 66 and the contact 1 of the deck 56. After thepulse is completed, the de-energization of the coil 51, which becameenergized when the contact 23 closed along with contact 27, causes eachof the arms 66, 67 and 68 of the stepping relay 55 to advance one stepto contact 2 of their respective decks 56, 57 and 58. The receipt of thesecond pulse (2), which is also low, places a ground on the movable arm66 and the contact 2 of the deck 56, and after the pulse is completed,causes the arms 66, 67 and 68 to advance to contact 3 of theirrespective decks S6, 57 and 58.

The third pulse (3), which is high and wrong, places a ground on themovable arm 67 and the contact 3 of the deck 57. The pulse is wrongbecause it causes a ground to be placed on the lead 59. The grounding ofthe lead 59 is how the stepping relay 55 recognizes that the codesequence is wrong, as will now be explained. It can be seen that foreach step of the stepping relay 55, either the contact of the deck 56 isconnected to the lead 59 and the other one is left unconnected, or viceversa. For the proper code sequence the pulses will so energize therelays 25 or 35 that as the stepping relay 55 advances, the lead 59 isnever grounded by the movable arm 66 or 67; or stated another way, forthe proper code sequence, the arm 66 or 67 which is grounded at eachstep is the one whose respective contact is left unconnected. Thisproper code sequence permits the stepping relay 55 to continue toadvance in order to provide the desired operation. But when the lead 59is grounded because of a wrong pulse, as is the case for the third pulse(3) of the assumed wrong code as described above, the coil 81 of thecode check relay 85 becomes energized, since one of its ends isconnected to a grounded power source represented by the battery 210 andits other end is connected to the lead 59.

When the code check relay 85 is energized by the placing of a ground onlead 59 as the result of a wrong pulse, the following functions areperformed: (a) the moving arm element 860 of contact 86 moves to thefixed element 86b to keep the lead 59 grounded through the normallyclosed contact 72 of the time relay 75, thereby keeping the relay 85closed regardless of whether or not the lead 59 is grounded by a movablearm 66 or 67; because the stepping relay is of the type which advancesonly after the energization pulse to coil 51 is removed, ample time isavailable to permit the contact 86 of the relay 85 to operate; (b) themovement of the moving arm element 86a from the fixed element 86cprevents further incoming pulses of energy from energizing the coil 51of the stepping relay by removing the ground from the common fixedelements 23b and 33b of relays 25 and 35, respectively; (c) the movingarm element 87a of the contact 87 disconnects from the fixed element870, which is connected to the movable arm 68 of the deck 58 and whichperforms the arming, firing and safing functions, as will hereinafter bedescribed; (d) the movement of the grounded moving arm element 87a tothe fixed element 87!: places a ground on the normally closedinterrupter contact 52 of the stepping relay 55, causing the steppingrelay to "free-run itself to its home position (no. 1), where the homecontact 53 (which is in series with the interrupter contact 52 andremains closed except in the home position) opens to terminate thisfree-running action; (e) the movement of the grounded moving arm element88a of the contact 88 to the fixed element 88b energizes the coil 71 ofthe 3-minute time delay relay 75, since one end of the coil 71 isconnected to the grounded battery 210 and the other end is connected tothe fixed element 88b; (f) the movement of the grounded moving contactelement 88a away from the fixed element 88c breaks the ground circuit tothe coil 41 code reversing relay 45 so that if the relay 45 had beenenergized, it would be unlatched by the operation of the contact 88; theoperation of the code reversing relay 45 is fully described inconnection with the description of the safing function of the circuit;(g) the closing of the normally open contact 89 closes the input lead153 to the firing circuit 150 with which it is in series.

From the above description, it can be seen that as soon as a wrong pulseis received, the code check relay energizes, disabling the arming,firing and safing functions and causing the stepping relay 55 tofree-run to its home (no. 1) position. The continued energization of thecode check relay 85 maintains the circuit inoperative until thethree-minute time delay relay 75 operates, opening the normally closedcontact 72, thereby deenergizing the coil 81. The provision of the timedelay relay 75 is useful to prevent the enemy from continuouslyoperating the above-described error-check system in the event they knewthe predetermined carrier frequency of the master station 10 so as toreduce the life of the batteries or damage the mechanism by constantstarting and resetting operations. A 3'minute time delay, such asprovided by the relay 75, permits the enemy to cycle the equipment only20 times an hour.

lfa noise burst were to pass through the receiver 12 with the relay 55in its home (no. 1) position, as might happen during an electricalstorm, and were to operate the correct relay 25 or 35, the steppingrelay 55 would advance to contact 2 and might remain there indefinitelywithout the sender at the master station 10 being aware of it. Or, themaster station 10 might start to transmit a code signal and fail to sendthe remainder of the sequence due to some difficulty, causing thestepping switch to remain at some intermediate contact. To prevent suchpossibilities, the one-minute time delay relay 105 and the relay areprovided with their coils 101 and 91 connected in parallel through thenormally closed contact 106 of the time delay relay 105, each coilthereby having one end connected to the grounded battery 220 and theother end connected to the contact 2 of the deck 58 of the steppingrelay 55. Thus, if the stepping relay 55 remains at or passes thecontact 2, the relays and 95 will both be energized, the normally closedcontact 96 of the relay 95 keeping the coils 101 and 91 energized, evenwhen the stepping relay 55 advances past the contact 2. After oneminute, the time delay relay 105 operates, causing the normally opencontact 107 to apply a ground to the lead 59, thereby energizing thecode check relay 85 and causing the stepping switch to free-run to thehome position (no. 1), as previously described. Also, when the timedelay relay 105 operates, the normally closed contact 106 opens,de-energizing the coil 91 of relay 95, which opens the contact 96,thereby also de-energizing the time delay coil 101. The time that thecontact 107 is closed so as to ground the lead 59 should obviously bemade long enough to permit the code check relay 85 to become energized.It is evident, therefore, that if the stepping relay 55 unintentionallyleaves the home position, the action of the relays 95, 105 and 85 willagain return the stepping relay to the home position after 1 minute, andthe circuit will be ready to receive a code sequence 3 minutes laterwhen the 3-minute timli delay relay 75 operates to open the relay 85.This action is also used to prepare the circuit to receive the firingcode sequence after it has been armed, as will hereinafter be described.

If it is now desired to arm the munition, 19 pulses of high and lowfrequency energy having the correct code sequence, as given previously,are transmitted to the munition control circuit from the master station10, advancing the stepping relay 55 to contact 20, thereby causing themovable arm 68 of deck 58, which is connected to ground through thecontact 87 of relay 85, to apply a ground to the munition arming circuit190. The munition arming circuit 190 is adapted so that the applicationof this ground thereto activates the circuit 190, causing it to arm themunition, in accordance with well known arming techniques. The 19correct pulses are sent in about 40 seconds so that about 20 secondslater, the action of the relays 95, 105 and 85 causes the stepping relay55 to free-run back to its home (no. 1) position.

When the time delay relay 75 opens about three minutes later, thecircuit is ready to receive the coded sequence which will fire themunition. The sequence, which the master station now transmits in orderto fire the munition, consists of a sequence of 21 correct pulses ofhigh and low frequency energy as given above, and then one deliberatewrong pulse of high frequency energy as the twenty-second pulse of thesequence. The 21 correct pulses advance the stepping relay 55 to contact22, causing the movable arm 68 of the deck 58 to ground one end of thecoil 111 of the firing relay 115 whose other end is connected to thegrounded battery 250 through the normally closed contact 48 of the relay45. The firing relay 115 thus becomes energized and the contact 116thereof latches the relay 115 in the energized position, while thecontact 117 thereof applies the voltage of the grounded battery 200 toone of the elements of the contact 89 of the code check relay 85. Whenthe code check relay 85 is energized by the incorrect twenty-secondpulse, therefore, the closing of contact 89 applies the voltage of thebattery 200 to the firing circuit 150, thereupon causing the firingcircuit 150 to apply a pulse to activate the detonator 170 and detonatethe munition. The total time taken for the stepping relay 55 to advanceto the contact 23 is obviously made less than 1 minute, otherwise theaction of the l-minute time delay relay 105 and the relays 95 and 85would return the stepping relay 55 to the home position before firingoccurred. From the description of the firing operation, it will beunderstood that a fail-safe situation is achieved because both a correctcode and at least one error code is necessary to activate the firingcircuit 150.

In the event that it is desired to place the munition in a safecondition so that it can be handled without the anti-disturbance device160 activating the detonator 170, the master station 10 transmits asequence of 14 correct pulses of high and low frequency energy, therebyadvancing the stepping relay 55 from its home (no. 1) position to thecontact 15, causing the movable arm 68 of deck 58 to ground one end ofthe coil 131 of the 3-second time delay relay 135 whose other end isconnected to the grounded battery 200. Three seconds after the steppingrelay 55 advances to contact 15, therefore, the normally open contact136 of the time delay relay 135 closes, grounding one end of the coil 41of the code reversing relay 45 whose other end is connected to thegrounded battery 220. The code reversing relay 45 thus becomes energizedand latches itself in the energized position by means of the contact 49which provides a ground through the contact 88 of the code check relay85. Thus, if an error in transmission should occur, or an error beintroduced by a noise burst, the energization of the code check relaywould unlatch the code reversing relay 45 so as to per mit the circuitto return to its initial conditions. The 3- second time delay relay 135is necessary, because in the arming and firing sequences described thestepping relay 55 must pass the contact 15 without operating the relay135 or the code reversing relay 45. Since in normal operation the armingand firing sequences are transmitted at a rate of about one pulse every0.2 second, the 3-second time delay relay 135 will not operate toenergize the code reversing relay 45 unless the stepping relay 55 isdeliberately stopped for at least 3 seconds at the contact 15.

When the 3-second time delay relay 135 operates, causing the codereversing relay 45 to also become energized, contacts 46 and 47 operateto reverse the code provided by the stepping relay 55; it can be seenthat this is accomplished by the contact 46 switching the movable arm 66of the deck 56 from the output of the low tone relay 25 to the output ofthe high tone relay 35, and the contact 47 switching the movable arm ofthe deck 57 from the output of the high tone relay 35 to the output ofthe low tone relay 25. Also, the opening of the normally closed contact48 by energization of the code reversing relay 45 causes the end 111a ofcoil 111 of the relay 115 to be disconnected from the grounded battery250, thereby disabling the firing relay 115.

in transmitting the safing code sequence, the stepping relay is held atthe contact 15 for about 5 seconds to permit the 3-second time delayrelay to operate, the remainder of the safing code is now transmittedconsisting of 10 pulses of high and low frequency energy to advance thestepping relay 55 from the contact 15 to the last contact 25. Becausethe code provided by the stepping relay 55 has been reversed by the codereversing relay 45, these 10 pulses, corresponding to pulses (15) to(24) of the correct sequence of pulses previously given, must be wrongin order to advance the stepping relay to the last contact 25. Atcontact 25, the grounded movable arm 68 of deck 58 grounds one end ofthe coil 121 of the safing relay 125 whose other end is connected to thegrounded battery 250, thereby energizing the safing relay 125, thecontact 126 permanently latching the safing relay 125 in an energizedcondition. The contact 127 of the safing relay 125 disables theanti-disturbance device by disconnecting the power source represented bythe grounded battery 200 from the input of the device 160. Also, thecontact 127 connects the battery 200 to activate the transmitter 180,causing it to radiate a predetermined signal to the master station 10,where it is received by the receiver 17 and appears on the indicator 24to inform the sender that the munition has been made safe. If thispredetermined signal is not received, the sender must try a second time,or more, to safe the device.

It can be seen that the safing operation of the circuit is such thatbecause the stepping relay 55 is required to stop at the contact 15 fora predetermined time (3 seconds) to disable the firing circuit andreverse the code provided by the relay 55, any chance of accidentallyfiring the munition during the safing operation is eliminated. Forexample, if the stepping relay 55 had stopped at the contact 15 and thenthe master station 10 continued to send a proper firing code sequence byerror, or because of some difficulty every pulse after the contact isreached is in error, the stepping relay would be returned to its homeposition by action of the code check relay 85.

From the above description of a munition control circuit in accordancewith the invention, it will be evident to those skilled in the art thatthe coding principle of this invention provided by the stepping relay 55and the associated components is very flexible and easily permitschanging or adding more codes. With the addition of a third tone relayto the relays and 35 and another deck provided on the relay 55, forexample, the number of possible combinations can be greatly increased.In the present stepping relay using two decks 56 and 57 each having 25contacts to supply the code over thirtythree million combinations areavailable, while by using another tone relay and another deck, overeight hundred billion combinations would be available.

It should be noted that the above-described munition control circuit canbe made amazingly simple and compact in view of the many, many possiblecombinations and variations of codes that are made available. It shouldalso be noted that, in the standby condition, the circuit consumes nopower from the batteries, and if so desired the batteries could becombined into a single power supply by suitable choice of operatingvoltages for the various components.

It will be understood, therefore, that the illustrative embodimentdescribed is only exemplary and that various modifications can be madein construction and arrangement within the scope of the invention asdefined in the appended claims.

I claim as my invention:

1. A munition safing, arming and firing system comprising means fortransmitting a code consisting of pulses of differing frequencies, meansfor receiving said code, means for segregating the received pulsesaccording to frequency, a stepping relay having a plurality of contactdecks each of which corresponds to one of the frequencies contained insaid code and one additional contact deck, each of said contact deckshaving an associated wiper arm, said wiper arms being ganged forconjoint movement, means connected to said segregating means forapplying ground potential to only one of the wiper arms of saidplurality of contact decks in response to a pulse of the correspondingfrequency, means interconnecting the contacts of said plurality ofcontact decks in correspondence with a preselected code, switch meansfor advancing said wiper arms one contact position in response to eachpulse received by said receiving means, code check means connected tosaid interconnecting means for free-running said stepping switch back toits initial position after a predetermined time delay in response to apulse which deviates from said preselected code, time delay meansconnected to said code check means for free-running said stepping relayback to its initial position after a predetermined time independently ofthe receipt of an incorrect pulse, arming circuit means connected to apredetermined contact of said additional contact deck, firing circuitmeans connected to a contact succeeding said predetermined contact andto said code check means so that upon the receipt of a correct series ofpulses followed by an incorrect pulse the firing circuit will beactivated through said code check means.

2. The device of claim 1 in which there is additionally provided codereversing means for causing said code check means to respond to acorrect rather than an incorrect pulse and switch means responsive tothe deliberate stopping of said wiper arms at a predetermined contactfor a preselected length of time for activating said code reversingmeans.

1. A munition safing, arming and firing system comprising means fortransmitting a code consisting of pulses of differing frequencies, meansfor receiving said code, means for segregating the received pulsesaccording to frequency, a stepping relay having a plurality of contactdecks each of which corresponds to one of the frequencies contained insaid code and one additional contact deck, each of said contact deckshaving an associated wiper arm, said wiper arms being ganged forconjoint movement, means connected to said segregating means forapplying ground potential to only one of the wiper arms of saidplurality of contact decks in response to a pulse of the correspondingfrequency, means interconnecting the contacts of said plurality ofcontact decks in correspondence with a preselected code, switch meansfor advancing said wiper arms one contact position in response to eachpulse received by said receiving means, code check means connected tosaid interconnecting means for freerunning said stepping switch back toits initial position after a predetermined time delay in response to apulse which deviates from said preselected code, time delay meansconnected to said code check means for free-running said stepping relayback to its initial position after a predetermined time independently ofthe receipt of an incorrect pulse, arming circuit means connected to apredetermined contact of said additional contact deck, firing circuitmeans connected to a contact succeeding said predetermined contact andto said code check means so that upon the receipt of a correct series ofpulses followed by an incorrect pulse the firing circuit will beactivated through said code check means.
 2. The device of claim 1 inwhich there is additionally provided code reversing means for causingsaid code check means to respond to a correct rather than an incorrectpulse and switch means responsive to the deliberate stopping of saidwiper arms at a predetermined contact for a preselected length of timefor activating said code reversing means.